Wet etching was the standard pattern transfer technique used to fabricate early generations of integrated circuits. Its widespread use arose because the technology of wet etching was well established and understood. Further, liquid etchant is available with very high selectively to both the substrate and the masking layer. However, wet etching processes are typically isotropic, which is unsuitable for many applications.
One alternative pattern transfer method that offers the capability of non-isotropic etching is dry etching. Dry etching also offers the important manufacturing advantage of eliminating the handling, consumption, and disposal of the relatively large quantities of dangerous acids and solvents used in wet etching and resist stripping processes. Dry etching and resist stripping operations use comparatively small amounts of chemicals.
The Rainbow 4520 manufactured by Lam Research Corp. is a machine that performs oxide, polysilicon, and nitride dry etching. The Rainbow 4520 is an older machine that has been in service for a number of years. One issue for the Rainbow 4520 is that through extended use, some elements of the Rainbow 4520 age and degrade. This degradation often manifests itself in the auto-resetting of the Rainbow 4520. As can be appreciated, this event will seriously adversely impact the operations of the Rainbow 4520. The auto-reset sequence causes a significant amount of down-time while the machine re-initializes, waits for temperature stabilization, and reassigns recipe parameters.
If the auto-reset occurs during a dry etch run, the conditions within the dry etch chamber will be uncontrolled, which will degrade the yield of the wafer, and furthermore, a great deal of wafers may be useless. Unfortunately, many spare parts for the Rainbow 4520 are not produced any more, which implies that repairs to those parts are now the user's responsibility. What is needed is an apparatus that prevents the auto-resetting of the Rainbow 4520.